Michael had some chocolate chip cookies and vanilla cookies. He gave away 100 cookies to his cousin. 10% of them were chocolate chip cookies and the rest were vanilla cookies.

1. How many vanilla cookies did he give his cousin?
2. Michael gave some chocolate chip cookies to his brother. ⁵₇ of all the cookies he gave away to his cousin and his brother were chocolate chip cookies. How many chocolate chip cookies did he give his brother?

(a)
Percentage of vanilla cookies
= 100% - 10%
= 90%

Number of vanilla cookies that Michael gave to his cousin
= 90% x 100
= ⁹⁰₁₀₀ x 100
= 90 

(b)
Fraction of all the cookies he gave away to his cousin and his brother that were vanilla cookies
= 1 - ⁵₇
= ²₇

2 u = 90

1 u = 90 ÷ 2 = 45

Number of chocolate chip cookies that Michael gave to his cousin and his brother
= 5 u
= 5 x 45
= 225

Number of chocolate chip cookies that Michael gave to his cousin
= 100 - 90
= 10

Number of chocolate chip cookies that Michael gave to his brother
= 225 - 10
= 215

Answer(s): (a) 90; (b) 215